Reality TV star Brandi Glanville admits she wanted to "kill" singer LeAnn Rimes, who ran off and married Glanville's ex-husband, Eddie Cibrian, and now acts as stepmother to Glanville's children.

"I thought I was going to physically hurt her," said Glanville, in an interview with Radar Online, after Rimes turned up at soccer games to see Glanville's boys, Mason, 8, and Jake, 5, play.

"I remember walking up to soccer practice and there she was with my baby in her lap," said Glanville, one of the "Real Housewives of Beverly Hills." "My blood was boiling, and I thought I was going to kill her. I really thought I was going to physically hurt her. … She was sitting in my soccer chair, under my tent. She's got my kid on her lap, and she's with my husband, and that was that little moment of total irrational fury."

In a culture in which half of all marriages end in divorce, stepchildren and half-siblings and the interplay of emotions between wives can wreak havoc on a mother's feelings, said Judy Kuriansky, a psychologist and relationship expert at Teachers College at Columbia University.

"It's really a normal feeling, but the obviously normal response is not to say it," said Kuriansky. "But the feeling is common - anger, resentment, the sense of betrayal, and to have to deal with the emotions on your own.

"Hell hath no fury like a woman scorned," she said. "You want to get rid of the woman who sabotaged you."

Glanville was married to Eddie Cibrian for eight years before he had an affair with Rimes while filming the Lifetime movie "Northern Lights" in 2009. First there were denials, but then came the incriminating photos. The two soon divorced their respective spouses and married each other in 2011. Rimes had been married to Dean Sheremet.

"This is what movies and TV shows are made of," said Kuriansky.

Real-life jealousy does, indeed, make for great fictional drama. On the latest episode of AMC's "Mad Men," wife No. 1 Betty Draper stirs up trouble with wife No. 2 Megan Draper after her three children spend a weekend at Don Draper's lush Manhattan apartment.

Betty, who is unhappily married and has ballooned up from her model figure, spies lean and sexy Megan in a state of undress while picking up her children. Back at home, Sally asks for help on a family tree project and Betty reveals that Don had a third wife. "Ask Megan about it," she tells Sally, cryptically.

Confused and feeling betrayed by not knowing the truth and feeling as if she's been used as a weapon by her mother, Sally lashes out at all her parents for keeping secrets.

Both the real housewife Glanville and the fictional character Betty Draper see the new, beautiful family unit replacing the crumbling old one.

"The family looks so happy with the good-looking husband and the children in tow," said Kuriansky. "That would press anyone's button."

But, she warns, parents should take care not to suck their children into the angry vortex.

"And it's not just mommies, but daddies, too," Kuriansky said. "Any parent who sees another treating their children as their own would act the same way. It's territorial and anthropological."

"It's normal to have the mama bear feeling," said Kuriansky. "Anyone who gets near, you want to kill, especially if the [step-mother] is really close. … But it's always the children who suffer, because they are torn. Be careful not to use them as weapons. In a healthy environment, the parents work it out."

As for Don and Betty Draper, tune in next week to see how their rivalries get resolved - or escalated.

But for Glanville, she admits that she is no longer so upset with Rimes.

"We're never going to be best friends," she told Radar Online. "But she's good to my kids. They love her, and that's all I could ask for. If they didn't like her, I'd be in court right now, fighting. It's not about me - it's about them."